PEO Triblock Copolymers Research Articles

Synthesis of mesoporous Pt@KIT−6/SAPO−11 VIA in situ encapsulation to catalyze the decarboxylation of oleic acid to C8–C17 alkanes

AbstractBACKGROUNDA series of mesoporous Pt@KIT−6/SAPO−11 catalysts with SiO2:Al2O3 molar ratios of 0.3, 0.4, or 0.5 and Pt loadings of 0.4, 0.8, or 1.2 wt% were prepared via an in situ encapsulation process using a PEO − PPO − PEO triblock copolymer (EO20PO70EO20, P123) as the mes. China 750001 oporous template and KIT−6 molecular sieves as the silicon source.RESULTSThese catalysts were characterized by transmission electron microscopy (TEM), specific surface area analysis, and pyridine–infrared spectroscopy (Py − IR). The results showed that Pt nanoparticles with particle sizes of 3–7 nm were uniformly dispersed on the supports. These materials also exhibited good mesoporous structures with specific surface areas of 138–197 m2/g and average pore sizes of 7.1–9.9 nm. The specimens having a SiO2:Al2O3 molar ratio of 0.4 also showed an orderly strip−shaped pore structure. The Py − IR results indicated that the catalysts had both Brønsted acid and Lewis acid sites, with total acid contents in the range of 77.8–131.1 μmol/g.CONCLUSIONThe decarboxylation of oleic acid using these materials under CO2 was examined. The catalyst with a SiO2:Al2O3 molar ratio of 0.4 and a Pt loading of 0.8 exhibited the best catalytic performance and a C8 − C17 alkanes yield as high as 85.1% at 340 °C by using a catalyst−to−oil mass ratio of 1:10 and a reaction time of 5 h. This performance was attributed to the ordered mesoporous structure of this catalyst along with its high surface area (173 m2/g), good crystallinity (92.8%), suitable acid content (98.6 μmol/g), and abundant Pt metal active sites. © 2022 Society of Chemical Industry (SCI).

T908 Polymeric Micelles Improved the Uptake of Sgc8-c Aptamer Probe in Tumor-Bearing Mice: A Co-Association Study between the Probe and Preformed Nanostructures.

Aptamers are oligonucleotides that have the characteristic of recognizing a target with high affinity and specificity. Based on our previous studies, the aptamer probe Sgc8-c-Alexa647 is a promising tool for molecular imaging of PTK7, which is an interesting biomarker in cancer. In order to improve the delivery of this probe as well as create a novel drug delivery nanosystem targeted to the PTK7 receptor, we evaluate the co-association between the probe and preformed nanostructures. In this work, preformed pegylated liposomes (PPL) and linear and branched pristine polymeric micelles (PMs), based on PEO–PPO–PEO triblock copolymers were used: poloxamer F127® and poloxamines T1307® and T908®. For it, Sgc8-c-Alexa647 and its co-association with the different nanostructures was exhaustively analyzed. DLS analysis showed nanometric sizes, and TEM and AFM showed notable differences between free- and co-associated probe. Likewise, all nanosystems were evaluated on A20 lymphoma cell line overexpressing PTK7, and the confocal microscopy images showed distinctness in cellular uptake. Finally, the biodistribution in BALB/c mice bearing lymphoma-tumor and pharmacokinetic study revealed an encouraging profile for T908-probe. All data obtained from this work suggested that PMs and, more specifically T908 ones, are good candidates to improve the pharmacokinetics and the tumor uptake of aptamer-based probes.

Structural Study of the Hydration of Lipid Membranes Upon Interaction With Mesoporous Supports Prepared by Standard Methods and/or X‐Ray Irradiation

Mesoporous materials feature ordered tailored structures with uniform pore sizes and highly accessible surface areas, making them an ideal host for functional organic molecules or nanoparticles for analytical and sensing applications. Moreover, as their porosity could be employed to deliver fluids, they could be suitable materials for nanofluidic devices. As a first step in this direction, we present a study of the hydration of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) model lipid membranes on solid mesoporous support. POPC was selected as it changes the structure upon hydration at room temperature. Mesoporous films were prepared using two different templating agents, Pluronic P123 (PEO–PPO–PEO triblock copolymer where PEO is polyethylene oxide and PPO is polypropylene oxide) and Brij 58 (C16H33(EO)20OH where EO is ethylene oxide), both following the conventional route and by X-ray irradiation via deep X-ray lithography technique and subsequent development. The same samples were additionally functionalized with a self-assembly monolayer (SAM) of (3-aminopropyl)triethoxysilane. For every film, the contact angle was measured. A time resolved structural study was conducted using in situ grazing incidence small-angle X-ray scattering while increasing the external humidity (RH), from 15 to 75% in a specially designed chamber. The measurements evidenced that the lipid membrane hydration on mesoporous films occurs at a lower humidity value with respect to POPC deposited on silicon substrates, demonstrating the possibility of using porosity to convey water from below. A different level of hydration was reached by using the mesoporous thin film prepared with conventional methods or the irradiated ones, or by functionalizing the film using the SAM strategy, meaning that the hydration can be partially selectively tuned. Therefore, mesoporous films can be employed as “interactive” sample holders with specimens deposited on them. Moreover, thanks to the possibility of patterning the films using deep X-ray lithography, devices for biological studies of increasing complexity by selectively functionalizing the mesopores with biofunctional SAMs could be designed and fabricated.

Length of the Core Forming Block Effect on Fusion and Fission Dynamics at Equilibrium in PEO–PPO–PEO Triblock Copolymer Micelles in the Spherical Regime

The slow kinetics of block copolymer micelles make their dynamical pathways as important as the copolymer architecture in the self-assembly of nanostructures. Two types of dynamical pathways could ...

Quantifying Drug Cargo Partitioning in Block Copolymer Micelle Solutions

Understanding molecular partitioning in solution is crucial for the design of micelle-based formulations. We investigate PEO–PPO–PEO triblock copolymer micelles and their solubilization of three hy...

Self-Assemble Amphiphilic PEO-PPO-PEO Tri-Block Co-Polymeric Methotrexate Nanomicelles to Combat MCF7 Cancer Cells.

Methotrexate (MTX) is a water-insoluble, anti-tumor agent that causes adverse effects like bone marrow suppression, chronic interstitial obstructive pulmonary disease, hepatotoxicity, leukopenia, interstitial pneumonitis and nephrotoxicity with slow drug release rate. The present study aimed to successfully incorporate MTX into novel-targeted Pluronic (PEOPPO- PEO tri-block co-polymer) F127 polymeric micelles intended for intravenous administration with improved drug loading and sustained release behavior necessary to achieve better efficacy of MTX. MTX-loaded Pluronic F127 micelles were characterized for critical micelle concentration, particle size and zeta potential,1H NMR, drug loading, encapsulation efficiency characterization, cell uptake, in vitro release study along with partition coefficient and solubilization thermodynamics. The micellar formulation resulted in nano size 27.32±1.43nm of PF127/SDS, as compared to Pluronic F127 micelles or PF127/Phosphatidyl choline which were 30.52±1.18nm and 154.35±5.5nm in size, respectively. The uptake of PF127/SDS micellar formulation incorporating Rhodamine 123 in MCF7 cancer cells was found to be higher (84.25%) than PF127/PC, PF127 and MTX i.e. 66.26%, 73.59% and 53% respectively. The in vitro MTX release from PF127, PF127/SDS and PF127/PC polymeric micelles formulations was observed to be 69%, 69.5% and 66% at 12 h whereas 80.89%, 77.67% and 78.54% after 24 h, respectively and revealed a sustained release. MTX-loaded PF127/SDS micelles showed high partition coefficient and negative free energy of solubilization compared to PF127 and PF127/PC which signify self-assembly behavior and thermodynamic stability towards higher dissociation. It was finally concluded that MTX-loaded PF127/SDS micelles act as a potential anticancer delivery system in comparison to PF127/PC and PF127 to combat tumor cells by enhancing their cellular uptake targeting with sustained release pattern and reducing the thermodynamic instability. Thus, PF127/SDS micellar formulation can provide a useful alternative dosage form for intravenous administration of MTX.

Influence of surfactant's polar head group charge on the self-assembly of three PEO–PPO–PEO triblock copolymers of widely varying hydrophobicity

The present study is based on the interaction between three polyethylene oxide-polypropylene oxide-polyethylene oxide (PEO-PPO-PEO) triblock copolymers namely Pluronics® L81, P84 and F88 (with same PPO Mol. Wt. but 10,40 and 80% PEO, respectively) and the ionic surfactants with 12-C chain but different polar head group charge viz. sodium dodecyl sulfate (SDS, anionic), dodecyl trimethylammonium bromide (DTAB, cationic) and N-dodecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (C12PS, zwitterionic) using plethora of techniques. The most hydrophobic Pluronic® L81 (cloud point, CP = 16.5 °C (5%w/w)) remains as molecularly dissolved below the CP and forms unstable vesicles close to CP, moderately hydrophobic, P84 (CP = 73.6 °C), remains molecularly dissolved below 15 °C and forms core-shell micelle above critical micelle temperature (CMT) and the highly hydrophilic F88 forms micelles at elevated temperatures. Micellization and dye solubilizing ability improved in the presence of salt (sodium chloride, NaCl). The presence of ionic surfactants leads to small sized surfactant rich micelles with progressive addition as confirmed by dynamic light scattering (DLS) and small angle neutron scattering (SANS). Amongst the three copolymers, P84 (Nagg ≈ 72) showed maximum solubility of dye and lowering power of CMC (CAC < 2 mM), hence SANS studies were limited to P84 and it was observed that SDS (Nagg ≈ 45) showed stronger interactions with P84 as compared to DTAB (Nagg ≈ 53) and C12PS (Nagg ≈ 83).

Relaxation Behavior and Nonlinear Surface Rheology of PEO-PPO-PEO Triblock Copolymers at the Air-Water Interface.

Surface dilatational viscoelasticity of adsorbed layers of pluronics triblock copolymers at the air-water interface was measured using the oscillating barrier technique. The effect of molecular architecture and concentration on surface viscoelasticity was explored for two different types of pluronics with different degrees of hydrophobicity, Pluronic F-108 (Mw ≈ 14 600 g/mol) and Pluronic P-123 (Mw ≈ 5800 g/mol), the former exhibiting a larger hydrophilic to hydrophobic block length ratio. Frequency sweeps in the linear regime suggested that interfacial films of F-108 have higher surface limiting elasticity and larger in-plane and out-of-plane relaxation times at the same bulk concentration (the former possibly related to in-plane microstructure rearrangements, the latter to surface/bulk diffusion). Increasing the bulk concentration of pluronics from 1 to 100 μM led to a decrease in both in- and out-of-plane relaxation times. Large amplitude oscillatory dilatation (LAOD) tests were performed to capture nonlinear behavior of these interfacial films by means of elastic and viscous Lissajous plots. Nonlinearities in elastic responses were quantified through calculation of the strain-stiffening indices in extension SE and compression SC. Both pluronics exhibited strain softening in extension. In compression, P-123 showed strain-hardening and F-108 displayed a relatively linear response. Apparent strain hardening in extension was observed for the P-123 adsorbed film, at high strain, at a bulk concentration of 100 μM. However, at these strains, the response was dominated by the viscous contribution and calculation of strain rate-thickening factors in extension and compression showed that the overall response was strain rate-thinning in extension and strain rate-thickening in compression.

Porous Vesicles with Extrusion‐Tunable Permeability and Pore Size from Mixed Solutions of PEO–PPO–PEO Triblock Copolymers

AbstractBlock copolymer (BC) vesicles in aqueous solution can encapsulate hydrophilic molecules or nanoparticles for drug and gene delivery, enhanced imaging, microreactors, or sensors. Inexpensive, biocompatible poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide) (PEO–PPO–PEO) triblock copolymers (TBCs) would be ideal for these applications if they could form concentrated vesicle solutions to encapsulate such molecules with high efficiency. It is shown that solutions of two PEO–PPO–PEO TBCs (EO5–PO68–EO5 and EO100–PO65–EO100) form vesicles, that the vesicle membranes are permeable to low‐molecular weight (MW) solutes, and that extrusion reduces the membrane permeability and MW cutoff. Osmotic permeabilities before and after extrusion are ≈1000 and ≈10 µm s−1, respectively, while the MW cutoffs for solute rejection are ≈1000 and ≈400 g mol−1. Therefore, it is hypothesized that the vesicles contain pores, and that extrusion reduces the pores' size and the membrane's porosity. These selectively permeable vesicles can function as microreactors or sensors encapsulating large solutes without the need to add channel molecules or proteins.

Comicellization of Binary PEO–PPO–PEO Triblock Copolymer Mixtures in Ethylammonium Nitrate

The micellization of dilute solutions of Pluronic block copolymers P123 (EO20–PO70–EO20) and F127 (EO106–PO70–EO106) and comicellization of binary mixtures in partially deuterated ethylammonium nitrate (d3EAN, a protic ionic liquid) are studied by small-angle neutron scattering. The average Pluronics composition in micelles shows a linear dependence on the bulk Pluronic composition. The mole ratio between P123 molecules in the micelles to those existing as unimers in solvent increases with temperature and P123 concentration. At a fixed F127/P123 ratio, the micelle core radius, the micelle corona thickness, and the aggregation number decrease with increasing temperature, while the total micelle volume fraction increases. At a fixed temperature, increasing P123 content in the binary mixtures leads to a weak minimum in micelle core size and aggregation number and a weak maximum in micelle corona thickness and total volume fraction of micelles. The comicellization behavior in d3EAN resembles that in aqueous s...

Reduction of micellar size of PEO−PPO−PEO triblock copolymer in presence of ionic liquid in aqueous solutions: A SANS study

ABSTRACTThe interaction of ionic liquids (ILs) with non-ionic triblock copolymer, Pluronic® P123, in aqueous solutions has been investigated using Small Angle Neutron Scattering (SANS) measurements. The micellar structural parameters are obtained by fitting the SANS scattering data with model composed of core-shell form factor and a hard sphere structure factor of interaction, as a function of cationic head group of ILs. With the addition of ILs, a decrease in the micellar core, aggregation number, and hard sphere radius of P123 micelles was noticed. The results are discussed and explained as a function of cationic head groups of N-octylpyridinium/imidazolium chloride.

Incorporation of Lamotrigine Drug in the PEO–PPO–PEO Triblock Copolymer (Pluronic F127) Micelles: Effect of Hydrophilic Polymers

AbstractThe hydrophobic drug Lamotrigine (LTG) shows low bioavailability after oral administration. Work has been performed to improve the aqueous solubility of LTG using the micelles of amphiphilic block copolymers. Polyethylene oxide‐ polypropylene oxide‐ polyethylene oxide triblock copolymers (PEO–PPO–PEO), known as Pluronic®, have been the subject of current interest due to the versatile structural possibilities of varying PEO/PPO ratios. Incorporation of LTG in the aqueous micellar solutions of Pluronic® F127 was investigated using UV–visible spectroscopy. The shapes and size of the micelles with and without LTG have been ascertained using dynamic light scattering and small angle neutron scattering experiments. Results show increase in the Pluronic® micellar size with hard sphere radius with the incorporation of LTG. The effect of hydrophilic polymers (PEG1500 and F68) on the LTG‐incorporated Pluronic® F127 micelles was also studied and found inefficient for enhancement of the solubility of LTG. Solid forms of LTG‐incorporated Pluronic® F127 micelles with and without hydrophilic polymers, coded as LPMs, were successfully prepared through the thin‐film hydration method. Fourier transform infrared spectroscopy, X‐ray diffraction spectroscopy and thermogravimetric analysis have been used to ensure the compatibility of the LTG with Pluronic® F127 micelles in prepared LPMs. All the LPMs showed good incorporation efficiency, loading capacity and the sustained release profile of LTG. Results showed no specific improvement with the addition of hydrophilic polymers in the studied concentration range.

Preparation of highly ordered mesoporous ethane–silicas under weakly acidic conditions and their hydrothermal stability

Highly ordered mesoporous ethane–silicas were prepared in the presence of a PEO–PLGA–PEO triblock copolymer template using HCl, FeCl3·6H2O, and B(OH)3acidic catalysts and their hydrothermal stability was investigated in a closed aqueous system at 373 K for 4 weeks.

Interaction between bile salt sodium glycodeoxycholate and PEO–PPO–PEO triblock copolymers in aqueous solution

Bile salts can associate to PEO–PPO–PEO block copolymer micelles and disintegrate them depending on the relative block length and molecular weight of the copolymers and bile salt/copolymer molar ratio.

Effects of Bile Salt Sodium Glycodeoxycholate on the Self-Assembly of PEO-PPO-PEO Triblock Copolymer P123 in Aqueous Solution.

A comprehensive experimental study on the interaction between the PEO-PPO-PEO block copolymer P123 (EO20PO68EO20) and the anionic bile salt sodium glycodeoxycholate (NaGDC) in water has been performed. The work was aimed at investigating the suitability of using P123 as bile salt sequestrant beside the fundamental aspects of PEO-PPO-PEO block copolymer-bile salt interactions. Various experimental techniques including dynamic and static light scattering, small-angle X-ray scattering, and differential scanning calorimetry (DSC) were employed in combination with electrophoretic mobility measurements. The system was investigated at a constant P123 concentration of 1.74 mM and with varying bile salt concentrations up to approximately 250 mM NaGDC (or a molar ratio n(NaGDC)/n(P123) = 144). In the mixed P123-NaGDC solutions, the endothermic process related to the self-assembly of P123 was observed to gradually decrease in enthalpy and shift to higher temperatures upon progressive addition of NaGDC. To explain this effect, the formation of NaGDC micelles carrying partly dehydrated P123 unimers was proposed and translated into a stoichiometric model, which was able to fit the experimental DSC data. In the mixtures at low molar ratios, NaGDC monomers associated with the P123 micelle forming a charged "P123 micelle-NaGDC" complex with a dehydrated PPO core. These complexes disintegrated upon increasing NaGDC concentration to form small "NaGDC-P123" complexes visualized as bile salt micelles including one or a few P123 copolymer chains.

Role of PPO–PEO–PPO triblock copolymers in phase transitions of a PEO–PPO–PEO triblock copolymer in aqueous solution

The effects of two poly(propylene oxide)–poly(ethylene oxide)–poly(propylene oxide) (PPO–PEO–PPO) triblock copolymers, Pluronics-R 10R5 (PPO8–PEO22–PPO8) and 25R4 (PPO19–PEO33–PPO19), on the thermal and rheological properties as well as the phase transitions of a poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide) (PEO–PPO–PEO) triblock copolymer (Pluronic F127, PEO100–PPO65–PEO100) in aqueous solution have been systematically studied. Both 10R5 and 25R4 could shift the critical micellization temperature of F127 to lower temperatures, showing a “salt-out like” effect. When F127 itself is unable to form a gel at low concentrations, 25R4 could assist micelles of F127 to be connected into a gel network. However, 10R5 is too short to be able to assist F127 to form a gel. At low contents of 10R5 or 25R4, F127 dominates its gelation but 25R4 could affect the hard gel–soft gel transition while10R5 showed a weaker effect on the hard gel–soft gel transition than 25R4. The rheological scaling law in the vicinity of the gel point was examined to obtain the critical relaxation exponent n and the critical gel strength Sg. n decreases and Sg increases with increasing 25R4 at low concentrations of F127. However, 10R5 and 25R4 affected n and Sg differently at high concentrations of F127.

Micellar packing of pluronic block copolymer solutions: Polymeric impurity effects

Small angle X-ray scattering (SAXS), dynamic light scattering (DLS), and high performance liquid chromatography (HPLC) experiments are performed to support that the inter-micellar distance of Pluronic cubic structures in aqueous solutions is governed by the poly(ethylene oxide) (PEO)-poly(propylene oxide) (PPO)-PEO triblock copolymer concentration (not the overall polymer concentration) in the solutions. The “as-received (AR)” and “purified (Pure)” F108 solutions show a separate concentration dependence of body-centered cubic (BCC) lattice spacing, when the overall polymer concentration is used as a micellar packing parameter in aqueous solution. When the 22 wt% of non-micellizable polymeric impurities in the AR Pluronic F108 is taken into account, however, a universal concentration dependence of the BCC lattice spacing is observed, unifying results from both AR and Pure F108 solutions. When the PEO-PPO-PEO triblock copolymer concentration from the HPLC analysis is employed as an effective polymer concentration parameter, the universal relationship is observed to provide strong evidence that the polymeric impurities in AR F108 locate themselves in the less dense parts of the interstitial regions on the BCC lattice points, where were occupied by the triblock copolymer micelles. Although the polymeric impurities in AR F108 do not affect the actual triblock concentration dependence of the lattice spacing, they do shift the onset concentration of BCC micellar ordering. In the Pure F108, the onset of BCC packing occurs at the point where the nearest-neighbor radius (Rnn) in the BCC lattice is approximately equal to the hydrodynamic radius (Rh), indicating that lattice formation begins upon “hydrodynamic contact” between micelles. In the AR F108, the onset of packing occurs when Rnn/Rh is approximately 0.9, indicating that, in the presence of the polymeric impurities, micelles must be forced together beyond the point of hydrodynamic contact for the BCC packing. Open image in new window

Rheological Study of Order-to-Disorder Transitions and Phase Behavior of Block Copolymer–Surfactant Complexes Containing Hydrogen-Bonded Small Molecule Additives

Dynamic mechanical measurements were used to investigate the effect of small molecule additives on the order-to-disorder transitions (ODTs) of Pluronic, poly(ethylene oxide) (PEO)–poly(propylene oxide) (PPO)–PEO triblock copolymer surfactant melts. The small molecule additives contain multiple functional groups (carboxyl or hydroxyl), which selectively interact with the PEO component of Pluronic via hydrogen bonding, thereby effectively increasing χ of the system and leading to microphase separation in otherwise disordered melts. The ODTs of these Pluronic/small-molecule-additive complexes can be detected by rheology since, upon increasing temperature, crossing the order-to-disorder transition temperature (TODT) results in a sharp decrease in the low frequency storage and loss moduli (G′ and G″, respectively). The crystallization of the PEO component is suppressed with increasing additive loading due to strong hydrogen bond interactions. The TODT is strongly composition dependent and increases up to 145 °...

Effect of PEO–PPO–PEO triblock copolymers in the synthesis of magnetic nanoparticles embedded in SiO2 and TiO2 matrices by sol–gel method

Hematite and maghemite nanoparticles embedded in silica and titanium dioxide matrices were obtained by sol–gel method. A mixture of precursor solutions of SiO2 and TiO2 doped with Fe3O4 salt templated by the addition of PEO–PPO–PEO triblock copolymers in a concentration of 12.1 wt% PF127 (SiO2) and 4.1 wt% P123 (TiO2) produces very stable magnetic particles with average size between 5 and 10 nm. These neutral surfactants allow the control of the morphology and crystal phase of these magnetic nanoparticles, and stabilize the nanoparticles to avoid their aggregation. The samples were analyzed by X-ray diffraction, high-resolution transmission electron microscopy, and infrared and Mossbauer spectroscopies. Mossbauer results show that maghemite is the majority species in the SiO2 matrix (61.3 %) and TiO2 (63.0 %), respectively.

Modified release from lipid bilayer coated mesoporous silica nanoparticles using PEO–PPO–PEO triblock copolymers

Triblock copolymers comprised of poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide) (PEO–PPO–PEO, or trade name Pluronic) interact with lipid bilayers to increase their permeability. Here we demonstrate a novel application of Pluronic L61 and L64 as modification agents in tailoring the release rate of a molecular indicator species from 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) bilayer-coated superparamagnetic Fe3O4/mesoporous silica core–shell nanoparticles. We show there is a direct relationship between the Pluronics’ concentration and the indicator molecule release, suggesting Pluronics may be useful for the controlled release of drugs from lipid bilayer-coated carriers.